Today it is common for many receivers to use a Phase Locked Loop (PLL) driven internally by a Voltage Controller Oscillator (VCO) to generate a frequency and phase synchronized signal that may be used in a variety of signal generation activities such as down conversion, generating an intermediate frequency signal, isolation of a physical channel and/or demodulation of one of these into an analog or digital channel signal. Integrated circuits in the last few years have come to include these receivers in single components at what has often been a major savings in production cost. While these advances are impressive, there are some situations that must be accounted for. Integrated circuit manufacturing processes have some variations, often referred to as process variations that can affect the operation of the VCO. Additionally, the VCO's performance may vary with the ambient temperature within the integrated circuit. The central problem to be addressed here is how to cost effectively calibrate the VCO to take into account process variations and the ambient temperature of the integrated circuit at calibration time.
While it is well known that VCO's and the PLL's they support can be calibrated at the time of manufacturing and test, these calibration processes add to the manufacturing cost of the integrated circuits. Methods and apparatus are further needed that reduce the manufacturing costs while guaranteeing that these components will operate in their favored control voltage range given the ambient temperature and process variations encountered in making and operating the integrated circuit.